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#197742 - 12/17/10 09:32 PM 3 phase inverter  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
I've been asked to help facilitate the installation of a 10 kw 3 phase commercial pv system. There are some budget concerns. The inverters that we've looked at are quite expensive and are hoping there is a work around.
1. Can we use a single phase pv system that backfeeds the 3 phase main panel?

2. Can we use 3 single phase pv inverters and wire it in such a way that it is essentially the same as a 3 phase inverter? (someone told me you can)

I'm open to other suggestions.

Thanks,
Byron


Green Building & Alternative Energy Related:

#197746 - 12/17/10 11:39 PM Re: 3 phase inverter [Re: bwise121]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,799
Brick, NJ USA
Byron:
My opinions...

1: I strongly doubt that the POCO would allow you to grid-tie single into 3 phase.

2: I have not seen any attempt to do this. Theoreticaly it sounds feasible, like using three single phase transformers in lieu of a three phase transformer. Also, you may have issues with the AHJ, unless you can provide documentation (Mfg) of approved/listed use.





John

#197773 - 12/18/10 10:42 PM Re: 3 phase inverter [Re: bwise121]  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 781
Winchester, NH, US
What drove the decision that the system had to be 3 phase?

10 KW is a relatively small system. What size service are you looking to tie into?

Are there significant single phase loads off of the 3 phase service?


#197789 - 12/19/10 02:51 PM Re: 3 phase inverter [Re: LarryC]  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,313
Alaska
Many of the single phase inverters I dealt with can be wired as three phase. The problem is you are limited limited to one inverter per leg. Pending on the model, you could achieve 10kW. You won't be able to "stack" inverter so you would not be able to expand on it in the future if that was a future plan. Also as hotline1 mention, check with the POCO to see the system you plan to use is allowed to be grid tied


"Live Awesome!" - Kevin Carosa

#197835 - 12/22/10 06:38 PM Re: 3 phase inverter [Re: LarryC]  
bwise121  Offline
Member
Joined: Sep 2003
Posts: 114
Sacramento, CA USA
The service main is 600A 120/208 and there is one 225A 3phase, and two 100A single phase. Plenty of room for a small PV system.

Thanks!


#197851 - 12/23/10 08:38 PM Re: 3 phase inverter [Re: bwise121]  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 781
Winchester, NH, US
Originally Posted by bwise121
The service main is 600A 120/208 and there is one 225A 3phase, and two 100A single phase.


Assuming the 225A and 100A are designating sub panels off of the service, I would connect the inverter to the same PHASE as either one of the single phase panels. When the inverter is putting out current, it will help offset the unbalanced load.


#198216 - 01/16/11 12:07 AM Re: 3 phase inverter [Re: LarryC]  
moreDER  Offline
New Member
Joined: Jan 2011
Posts: 1
WA
The AHJ and the POCO would want a net metering set up, I'm pretty sure. So a separate production meter and all the signage and disconnects (lockable, window) etc. -

One idea would be to use the DC power for loads that want DC - computers, chargers, LED lighting (do a retrofit), DC motors, DC Thermal Heaters, etc. Transforming DC to AC to DC again is inefficient.



#198249 - 01/17/11 12:38 AM Re: 3 phase inverter [Re: bwise121]  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
Originally Posted by bwise121
I've been asked to help facilitate the installation of a 10 kw 3 phase commercial pv system. There are some budget concerns.

Byron,
Who designed this system, if it was eventually found that it couldn't be done with the capital available?
That is the keystone of any business venture, the brief to the system designer would (or should have been) do this with X$$$$$$, that is your starting point in any project.
Asking the technical staff to make compromises on the basis of lack of funds is not the best start to any project, no matter how large or small. crazy


Let's face it, these days if you're not young, you're old - Red Green grin

#198268 - 01/17/11 12:31 PM Re: 3 phase inverter [Re: moreDER]  
PAteenlectrician  Offline
Member
Joined: Jan 2011
Posts: 64
Cressona, Pa, U.S.A. (Schuylki...
Originally Posted by moreDER
One idea would be to use the DC power for loads that want DC - computers, chargers, LED lighting (do a retrofit), DC motors, DC Thermal Heaters, etc. Transforming DC to AC to DC again is inefficient.


That would still cost alot of money.



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